Wylfa 2 bows out

The penultimate Magnox reactor has generated its last electricity after 41 years of service. The closure of Wylfa 2 leaves its twin, unit 1, as the sole operational representative of the type.

Wylfa: last of the line (Image: NDA)

Wylfa 2 had been scheduled for closure on 30 April, but an operational issue forced it to close yesterday five days earlier than planned. Under normal circumstances the reactor would have returned to service within a few days, but it was decided not to restart because of the closeness to the scheduled shutdown date.

As the Magnox reactor program winds down, limited supplies of fuel prompted operator Magnox Ltd to decide to close Wylfa 2 in order to optimise operations at Wylfa 1, which is expected to continue in service until 2014. The plant received the final delivery of fresh Magnox fuel in December 2011 and Magnox Ltd has requested regulatory approval to transfer partially used fuel from unit 2 to unit 1, which is relatively simple thanks to a shared service floor and refuelling machine.

Magnox reactors are graphite-moderated, gas-cooled and use natural uranium fuel. They can trace their roots back to the earliest days of nuclear technology: the world's first commercial nuclear power station, Calder Hall, was a Magnox reactor, although they were initially envisaged as dual-purpose reactors combining the production of military plutonium with power generation. The design takes its name from the magnesium alloy cladding used on the uranium fuel. The UK built a fleet of 26 Magnox reactors of which Wylfa's two 490 MWe units, commissioned in 1971, were the last and the biggest.

Magnox reactors did not enjoy widespread adoption outside the UK, although two were sold to Italy and Japan, and six of France's first-generation gas-cooled, graphite-moderated reactors were of a very similar type. Wylfa became the last operating Magnox site after the closure of Oldbury 1 in February.

Wylfa stands on the Welsh island of Anglesey and is one of the sites included in the UK's nuclear new build plans. The RWE-EOn joint venture Horizon Nuclear Power had envisaged building up to four AP1000 reactors or three EPR units at the site, and a planning application was scheduled for submission later this year. However, the German utilities recently announced that they would not be going ahead with plans for new nuclear plants in the UK following strategic reviews prompted by Germany's abrupt change in nuclear policy and shutdown of reactors after the Fukushima accident.

Both RWE and EOn have been keen to emphasise that their decisions were a reflection of pressures in their wider business and not because of doubts on the future role of nuclear in the UK. The two companies are looking for a new owner for the Horizon joint venture.

Following Wylfa 2's closure the UK's operating nuclear park now comprises one Magnox unit, 14 advanced gas-cooled reactors and one pressurized water reactor.